linux-kernel - Re: [patch 2/3] nohz: change signal tick dependency to wakeup CPUs of member tasks

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Message-ID: <20210212141817.GA94816@lothringen>
Date:   Fri, 12 Feb 2021 15:18:17 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/3] nohz: change signal tick dependency to wakeup CPUs
 of member tasks

On Fri, Feb 12, 2021 at 11:00:41AM -0300, Marcelo Tosatti wrote:
> On Fri, Feb 12, 2021 at 01:25:21PM +0100, Frederic Weisbecker wrote:
> > On Thu, Jan 28, 2021 at 05:21:36PM -0300, Marcelo Tosatti wrote:
> > > Rather than waking up all nohz_full CPUs on the system, only wakeup 
> > > the target CPUs of member threads of the signal.
> > > 
> > > Reduces interruptions to nohz_full CPUs.
> > > 
> > > Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
> > > 
> > > Index: linux-2.6/kernel/time/tick-sched.c
> > > ===================================================================
> > > --- linux-2.6.orig/kernel/time/tick-sched.c
> > > +++ linux-2.6/kernel/time/tick-sched.c
> > > @@ -444,9 +444,20 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_ta
> > >   * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
> > >   * per process timers.
> > >   */
> > > -void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits
> > > bit)
> > 
> > Why not keeping the signal struct as a parameter?
> > 
> > Thanks.
> 
> All callers use "struct signal_struct *sig = tsk->signal" as
> signal parameter anyway...

Sure, but that makes more sense with the function role and name.

> 
> Can change parameters to (task, signal, bit) if you prefer.

That's ok I can do it, just wanted to make sure I wasn't missing
a reason behind it.

Thanks!